System for producing high density detergents



E. DAVIS 2,798,544

SYSTEM FOR PRODUCING HIGH DENSITY DETERGENTS July 9, 1957 Filed Feb. 28.1952 QL DA ws,

'IN V EN TOR. WW1 A TTOQNEY.

SYSTEM FOR PRODUCING HIGH DENSITY DETERGENTS Earl Davis, Whittier,Calif., assignor to Purex Corporation, Ltd., South Gate, Califw'acorporation or Caliu fornia Application February 28, 1952, Serial No.273,978

1 Claim. (Cl. 159-48) This invention has to do generally with themanufacture of detergents suitable for useI as washing compounds, andparticularly with the production of such compounded detergents bymethods having for their major object to give to the final andmarketable products desirable solubility properties and high bulkdensities. While applicable broadly to the manufacture of detergentcompositions in general and whose densities are subject to increase bydeaeration of a dryable slurry containing the detergent, the inventionwill be described typically, though as illustrative only, with referenceto detergents containing as active ingredients the alkali metal salts oforganic sulfonates and sulfates having such molecular structures as topossess detergent properties.

The` active ingredient may be any of various sulfonated or sulfatedcompositions of the following class: alkali metal (e. g. rhodium) alkylaromatic sulfonates such as the mono alkyl benzenes described in theLewis Patents Nos. 2,477,382 and 2,477,383, and also the alkylatednaphthalene sulfonates, such as dibutyl naphthalelne sulfonate, in allof which compounds the benzene or naphthalene radical is bonded to analkyl group containing from 8 to 18 carbon atoms; alkyl sulfonate saltsof the general formula R-SOa-X in which R (as in the formulas below) isan alkyl group containing 8 to 18 carbon atoms and X is an alkali metalsuch as sodium, for example lauryl sulfonate and cetyl sulfonate; alkylhydrogen sulfate salts of the general formula R-OSOa-X, e. g. sodiumoleyl sulfate and sodium lauryl sulfate; sulfated monoglycerides of thetype derived from coconut fatty acids and glycerine) such asR-COOCHz-CH-OH-CHz-OSOs-X sulfatedalkylolamides of fatty acids of thegeneral formula R-CO--NH-CHz-CHz-OSOa-X R-o o-N-oHr-CHn-SoaNa `Hasulfated amides of the formula R-CO-NH-CHz-OSOa-X or sulfonated amidesR-oo-N-cHg-CHPSOs-X (e. g. the product sold under the trade nameIgepon-T); sulfonated esters (such as Igepon-A) of the general formulaR-CO-OCl-lz-CHZSOa-X To any or mixtures of the foregoing may be addedany of the suitable alkylolamides in which the amide radical containsfrom 8 to 18 carbon atoms.

Suitable builders include the usualsalts including sodium sulfate,sodium carbonate, alkali metal silicates and any of variouspolyphosphates.

It has been customary in the manufacture of such detergents to producerst an aqueous slurry of the alkali metal organic sulfonates orsulfates, to which are added 4nited States Patent() f 2,798,544 PatentedJuly 9, 1957 one or more salts or additives such as soda ash, sodiumbicarbonate, alkali metal silicate, borax, sodium sulfate, sodiumchloride, fullers earth and the like, to produce a mixture or slurrydryable to any tinal form, e. g. as by spray drying, drum drying, ortray drying. Considering spray drying as typical, it is desirable thatthe solid granules resulting from spray drying of the slurry, have ahigh bulk density, say upward of 0.40 or above. Now by the usual methodsof slurry treatment and dehydration, potentially high bulk densities ofnal product either are not obtainable, or can be reached only as aresult of relatively inconvenient and prolonged procedures.

The use of packaged soaps and detergents, rather than bar soaps, forboth dish washing and the washing of cottons has progressed steadilyduring recent years. Both drum dried and spray dried types of productare packaged, with the preference for household use going to spray driedproducts because of their quicker solubility. One major limitation ofsuch products, especially the spray dried detergents, is that theirdensities are not high enough for the product to have maximumusefulness. lt is desirable that at least as much weight of the spraydried product be put into a box as is possible with granulated soap, butthis objective cannot be attained by conventional methods. In accordancewith the process disclosed in my Patent No. 2,606,156, issued August 5,1952, on Deaeration and Drying of Water Soluble Sulfonated DetergentCompositions, an important step toward achieving increased densities inthe dried detergent product is accomplished by deaeration of the slurrypreparatory to drying, as by passing the slurry from the mixer through azone maintained under subatmospheric pressure, typically 5 to 250 mm.absolute that may be regulated in accordance with the degree ofdeaeration desired.

A general object of the present invention is to provide a new system forcombined heating and deaeration of the slurry that affords improveddensity control and even greater ultimate densities in the final drying,and especially in a spray type drying operation. Heating alone haspreviously been tried, but found unsuccessful to any important degree,as a method for deaerating the slurry. The major and controllingditliculty found was that the consistency of mixes after theincorporation of the dry additives with the wet sulfonate, is such thateven under heat, the dissolved or occluded air does not leave the mix.Continuance of the heating in order to favor eventual removal of air isnot feasible because the presence of the detergent active ingredientscauses a steady thickening and gellation of the entire mass.Accordingly, the thickening and gelling effect has led to abandonment ofheating alone as a method of deaerating the slurry. l have nowdiscovered that the eticiency of vacuum deaeration can be improved andregions of density of the dried products otherwise unobtainable can bereached by controlled heating of the slurry in such relationships to thevacuum deaeration stage as will later be explained in detail,

The system may employ apparatus comprising a mixing chamber or zone inwhich an aqueous sulfonate slurry stream is thoroughly admixed with thesolid additives or builders, and an evacuated deaerating zone or chamberreceiving the slurry from the mixing zone and within which the slurry issubjected to division and extended particle or surface exposure,typically by spraying the slurry within an atmosphere maintained in theaforesaid 5 to 250 mm. absolute pressure range, at which a considerableand even major portion of the air leaves the slurry. The deaeration isaccompanied by water vaporization from the slurry, with the consequenttendency for the slurry to cool in proportion to thedegree of deaerationand water vaporization. From the Vdeaerating charnber the slurry ispumped to the drier, preferably through spray nozzles which disperse thedeaerated slurry in small droplets within the heated atmosphere of thedrier wherein final drying of the slurry occurs at the pressure at whichspray driers ordinarily are operated, that is, at about atmosphericpressure.

It is preferred that the aerated slurry going to the vacuum chamberlhave a temperature in the order of about 110 to 160 F. in order tocompensate for the tendency of the slurry to cool in the deaerator andthus preclude the possibility of excessive thickening of the slurryduring its deaeration. In the mixing of some detergents and builders,4as for example those having higher phosphate contents, suicient heat ofsolution rnayV be evolved as to raise the slurry temperature to withinthel desired temperature range. Where this is not the case, provisionmay be made for heating the sulfonate slurry in advance of the mixingzone, or the sulfonate and builder mixture Within lthe mixing zone, orbetween the mixing and -deaerating zones, so that the slurry will enterthe deaerating zone at a temperature within about the 110 to 160 F.range. In `general it is found desirable or necessary to .bring theslurry up to the desired temperature within this range, within a periodof time suciently short to avoid any consequential consistency increaseor gellation of the slurry due to heating. While the temperature ofserious gellation of any given slurry will be dependent upon itsparticular composition, it may be said that in general the slurrytemperature rise should occur within a period of time not to exceedabout 30 minutes.

It is found that the degree and eiectiveness of deaeration of the slurryin the evacuated zone are materially increased by reason of thepreheated condition. As an illustrative comparison, it has been observedthat a slurry entering the deaerating zone (absolute pressure about 50mm. of mercury) at a temperature of 150 F., lost twice the `amount ofair lost by the same slurry at a temperature around 110 F. passedthrough the deaerator under corresponding pressure.

With no further differences, the combined heating and deaerationcontemplated by the invention gives a finished dried product that isapproximately denser than it would be where the slurry temperatureduring deaeration was kept relatively low, e. g., in the neighborhood of100 F.

. The invention has a further and particularly important concept inproviding for heating of the slurry after its deaeration and withconsequent'temperature and uidity preconditioning that result in stillhigher densities of the dried product. As will be understood, where theslurry is not heated in advance of or within the deaerator, subsequentheating may compensate for any cooling of the slurry in the deaerator.In any event, heating of the slurry during itsrficw from the deaeratorto the drier within certain temperature limits directly favors thedesirable increased density of the product for a number of reasons,including, (l) uidizing or lowering the viscosity of the slurry ahead ofthe drier spray nozzle, with consequent lowering of the required nozzlepressure, the effect of which is to maintain larger average sprayedparticle size in the drier and therefore less dust in the product, (2)the number of pounds per hour of slurry that can be spray dried isincreased, (3) vdeaeration together with the heating is particularlybeneiicial in that heating of a slurry that has not been deaeratedresults in a puiy and non-uniform spray Iat the nozzle and consequentloss of particle size control, and-(4) vacuum deaeration and heatingpermit a temperature and time control which can be utilized to permitthe maximum eiective heat input to the slurry without exceeding thecritical temperature and time conditions that will result in itsgellation. As illustrative of specific heating conditions, it isfound-that the advantages of slurry heating immediately in advance ofthe spray drier may be realized by heating a stream of the `deaeratedslurry being pumped from the evacuated chamber to .the drier nozzles toa temperature in the vregion of to 190 F. over a controlled period ofbetween 5 to 100 seconds.

Heating of the slurry within or beyond the deaerating zone produces afluidizing etfect of which advantage is taken along with a condition ofat least practical similarity which is found to result `from deaerationof the slurry. It is found that the fluidity, or at least thepumpability of the deaerated slurry, all other conditions being equal,is greater or better than that of the same slurry not deaerated. Whilethe advantages of increased fluidity or better pumpability of thedeaerated slurry might be lost entirely or in part by excessive coolingin the deaerator, provision for heating the deaerated slurry assuresmaintenance and utilization of iluidizing effects and advantages of bothdeaeration and heating.

In certain types of spray drying towers slurries may be dried withindensity limits which are suitable as low density products', Withouteither deaeration or heating of the feed. If these slurries aredeaerated in the present type of spray `drying tower the densities aretoo high for light duty products, and heating within certain temperaturelimits will further increase the density outside of desirable limits.However, if the combination of heating and deaerating is such that thefeed temperature is about 240 F. the density is then reduced to a pointsuitable for light duty products. This accomplishes, then, theproduction of the desired product at a much increased tower capacity.

All the features and objects of the invention, as well as the structuraland method details of a typical commercially operable system, will bemore fully understood from the following detailed description of theaccompanying drawing, wherein the system is illustrated diagrammaticallyand in tiow sheet form.

A neutralized slurry, typically an aqueous sodium alkyl aryl sulfonateslurry, is delivered through line 24 for delivery to the mixer 25.Suitable solid builders or fillers are added Vthrough inlet 26 to theslurry in the mixer and the components are subjected to thorough mixingas by a mechanically driven agitator diagrammatically indicated at Z7.From typical operating data, it is found that the specified gravity ofthe neutralized slurry going to the mixer may be within the range ofabout 0.84 to 1.14. The sulfonated slurry after compounding with theadditives in the mixer and containing for example 8 to 50% by weight ofthe neutralized active detergent, has an increased density within therange of about 1.15 to 1.20. This slurry then is continuously withdrawnfrom the mixer through line 28 and discharged by pump 29 into adeaerating chamber 30 preferably in tinely divided or sprayed form, asthrough a spray nozzle 31 in the head of the chamber. The latter isconnected through line 32 with a suitable evacuator, so that thedeaerator is operated under a pressure considerably below atmosphericpressure, and typically within the range of 5 to 250 mm. absolute.Ordinarily the temperature of the compounded slurry will beapproximately atmospheric temperature. Being dispersed in finely dividedform within the evacuated zone, the compounded slurry is effectivelydepleted of its air content, as Well as some moisture, in accordancewith the pressure existing in the deaerator, and its Idensity is broughtwithin the range of say 1.20 to 1.44.

The deaerated slurry is continuously Withdrawn from the deaeratorthrough line 33 and is discharged by pump 34 into a suitable drier 35,preferably of the spray type within which the slurry is reduced to nelydivided form and dried by contact with hot gases or air, resulting inthe production of the detergent as granulzed particles. As previouslyindicated, the primary eiect and advantage of the deaeration is theproduction of-granules having higher bulk densities, this propertyapparently being due to theI f actthat whereasV ordinarily the presenceof air in the slurry being spray dried tends to remain entrapped and toexpand therein, thus enlarging the hollow globular particles andthinning the shells, preliminary removal of the air in accordance withthe invention enables the particles to dry in more compact and denseform, free from excessive air expansion.

The present invention is concerned primarily with the elects andadvantages gained by combined heating and deaeration of the slurry. Tothat end, provision may be made for heating the slurry in any convenientmanner, at the locations where heating is required in accordance withparticular conditions involved in a given instance.

Temperature conditioning of the slurry in the mixer by heat fromextraneous source, when required, may be eiected by steam taken fromline 36 to a jacket 37 about line 24 in advance of the mixer 25, or theslurry may be heated directly in the mixer as by steam supplied throughline 38 to the mixer jacket 39, or by direct injection through line 40into the slurry mass in the mixer. Heating in advance of or within themixer may in some instances be substituted by heating the slurry streambetween the mixer and the deaerator 30, as by means of a jacket 41 aboutline 2S and supplied with steam through line 42.

Where it is desired to heat the slurry while it undergoes deaeration,the chamber 30 may be enclosed within a jacket 142 to which steam is fedthrough line 43.

A particularly important provision for heating the deaerated slurrystream between the deaerator and spray tower, and preferably while thestream is being continuously discharged to the drier spray nozzle ornozzles 44, may be served by jaeketing at 45 the line 33 throughout asuicient length of line to raise the slurry temperature to the properlimit within a period of time suiciently short to prevent gellation inadvance of the nozzle 44. Steam is supplied to the jacket 35 throughline 46.

The showing at 35 is to be regarded as diagrammati cally illustrative ofany suitable type of spray drier within which the slurry beingdischarged from the spay nozzle is dried as by heated air circulatedthrough the ducts 145 and 146, the finally granulized dried productafter passing through the atmospheric cooling section 46 of the drierbeing discharged through outlet 47.

To cite a typical hatching procedure involved in making a low densitylight duty detergent, a slurry containing 4391 lbs. of water, 1636 lbs.of sodium sulfate and 2195 lbs. of sodium alkyl sulfonate was pumpedinto the mixing tank. The temperature of this slurry was brought toG-105 F. by injecting live steam up through the mix tank. To the slurrywas added 500 lbs. of water, 3900 lbs. of sodium sulfate and, finally 30lbs. of 93% sulfuric acid to bring the pH of the slurry down to 7.5-8.0.The mix tank agitator was kept running throughout the addition of thesematerials at such a rate that aeration of the slurry was minimized. Fromthe mix tank the compounded slurry was pumped through the vacuum tankfor deaeration at an absolute pressure of 50-75 mm. mercury. Finally thedeaerated slurry was pumped through line 33 tted with a steam jacket,which preheated the slurry to 125 F. before it entered the nozzles ofthe spray drying tower.

The following procedure may be used for producing a detergent of thephosphated heavy duty type: A high active slurry containing 9263 lbs.water, 1396 lbs. sodium sulfate and 5764 lbs. sodium alkyl arylsulfonate was heated to 10U-110 F. and pumped to the mix tank. In thisinstance the weight ratio of sodium alkyl aryl sulfcnate to sodiumsulfate is 4.1 to 1. To meet product specilication it was necessary tobring this ratio down to 3.4 to 1 by adding batchwise 300 lbs. of sodiumsulfate. This slurry was run into another mix tank where it was mixedcontinuously with 8564 lbs. of commercial sodium tripolyphosphate and4752 lbs. water. The temperature of the mix quickly rose to 11S-125 F.due to the hydration of the phosphate. After being continuously pumpedthrough the vacuum chamber the slurry was preheated to l-190 F. justbefore entering the nozzles of the spray drying tower. A spray driedproduct resulted which had a density in excess of 0.30 gm. per cc.

I claim:

The method of producing a bead form detergent that includes dispersingan air containing aqueous slurry of the detergent into the atmospherewithin a deaerating zone in finely divided form, maintaining said zoneat a sub-atmospheric pressure below about 250 mm. Hg absolute to removeair from the slurry, said sub-atmospheric pressure tending to cool theslurry by evaporation of moisture therefrom, then passing the slurry,including all ingredients thereof which enter the deaerating zone exceptfor air and vapors removed in said zone, into an independent spraydrying zone and therein spray drying the deaerated slurry to produce thedetergent in high density bead form, and heating said slurry in advanceof its entry to the spray drying zone to compensate for the coolingeffect of said sub-atmospheric pressure and thereby prevent thickeningof the slurry by said cooling, the detergent slurry fed to thedeaerating zone having a temperature between about F. and 160 F. wherebymaximum deaeration is effected, and the heating of the slurry in advanceof its entry to the spray drying zone being sufficient to maintain aslurry temperature between about F. and 190 F. immediately prior toentry of the slurry into the spray drying zone whereby a spray driedproduct of maximum density is obtained.

References Cited in the le of this patent UNITED STATES PATENTS Klepetkoet al. Apr. 28, 1953

